1. Field of the Invention
The invention generally relates to a method of substantially homogeneously mixing ingredients comprising solid particulates and a viscous material in a container. The invention also generally relates to a non-clogging device and mixing apparatus.
2. Background Art
Poly(ethylene terephthalate) (PET or polyethylene terephthalate) has many uses such as, for example, for making synthetic fibers and food-grade containers (e.g., beverage bottles). U.S. Pat. No. 7,297,721 B2; PCT International Patent Application Publication Number WO 98/41375 A; and Japanese Patent Application Number JP H10-101784 A all mention using homogeneous mixtures of recycled poly(ethylene terephthalate) (RPET) and poly(ethylene terephthalate) (PET) monomers comprising terephthalic acid (TPA) and monoethylene glycol (MEG) in processes to manufacture PET. Their processes all require melting the RPET to prepare the homogeneous mixtures and intimately expose the RPET to the full transesterifying affect of MEG, whereupon, among other things, the MEG depolymerizes the melted RPET by transesterification. For example, in U.S. Pat. No. 7,297,721 B2, the process adds a paste of TPA, isophthalic acid (IPA), and MEG to an esterification reactor, stops the addition, adds flakes of RPET, and then resumes adding additional paste. The RPET melts in the esterification reactor before fully mixing with the paste. In WO 98/41375 A, the process adds RPET as a melt or a solid to an esterification reactor containing a melt of PET precursors. The added solid RPET melts in the esterification reactor before fully mixing with the PET precursors. In JP H10-101784 A, the process melts RPET in an extruder, and then adds the melted RPET to an esterification reactor. The JP H10-101784 A process separately adds a slurry of TPA and MEG to the esterification reactor. In all of the aforementioned processes, the processes require melting RPET to form the homogeneous mixtures comprising RPET, TPA, and MEG so as to intimately expose the RPET to the full transesterifying affect of MEG.
As is generally known and known from the above-referenced patent documents, RPET gradually decomposes when it is near or above its melting temperature (e.g., RPET flakes melt at about 245 degrees Celsius). If left unchecked, melted RPET will decompose to an extent that it would become unsuitable for preparing food-grade PET.
There is a need in the art for an improved method of manufacturing PET using RPET.